Barentsz would not be persuaded that they had not been deceived, which caused wagers to be laid. The 25th and 26th there was too thick a fog to determine the dispute; but the 27th was a clear day, and the entire orb of the sun was seen above the horizon, whence there could remain no doubt that a part had been visible on the 24th. The journalist has been at pains to shew, that they had not erred in their reckoning of time, as might be conjectured from their having been so long without seeing the sun. Nothing is said of refraction, and probably it was not thought of, or was ill understood, and seldom allowed for in maritime observations at that early period.

From the 4th of November, when they wholly lost sight of the sun, to its reappearance, January the 24th, was eighty-one days. The middle time may be supposed the winter solstice, and the declination of the sun corresponding to forty and a half days from the time of the solstice, is 17° 24′ S. The latitude being 66° N. will give 93° 24′ for the distance of the sun (its centre) from the zenith, when its northern limb was first seen. Allowing 16' for the sun's semidiameter will leave about three degrees for the refraction and depression of the horizon, the latter of which was probably under a quarter of a degree. The effect

EFFECTS OF REFRACTION.

293

of the refraction then must have been not much less than three degrees.

In some other northern voyage it has been remarked, that the sun was seen twenty minutes sooner, and as much later, than the regular time of sun-rising and setting. Mr. Bayly, who sailed as astronomer in the last voyage of Captain Cook, related to me, that when he was assistant astronomer to Maskelyne, cattle which fed in a meadow on the opposite side of the Thames were visible from Flamstead House at high water, and hid by the bank at low water. The effect of refraction in giving apparent altitude to distant objects which are in reality below the horizontal level, appears in all these cases to have been many degrees.

As the water rose in the river, the objects on the farther side would be seen through a more dense medium, and the effect produced seems to have been giving apparently to the whole plain or surface beyond the river, an inclination or increase of inclination towards the beholder; the distant parts being the most refracted, as must be the case in the plain of a glacis so rendered visible, which is to be ascribed to the more distant object being seen through a longer extent of atmosphere. From similar causes it may be imagined that the apparent horizon at sea will

sometimes be a water-line more distant, and of course more elevated, than a true horizontal line.

Whether the real cattle were seen, or the increased density of the medium rendered it capable of receiving as in a mirror, and reflecting, the image of the cattle, is a very disputable question. The mind is not well satisfied with the hypothesis of inflected or bent rays and circuitous vision; a difficulty likewise not easy to surmount, is to explain how a thing may be seen where it is not. The image of an object which is not within an unobstructed right line of vision is frequently receiv d by a long train of reflections, every stage of which is distinguishable, or clearly traceable, from the substance to the eye of the beholder. Appearances of distant objects in the horizon are seen through a great length of the most dense part of the atmosphere, which may be capable of communicating the image of an object by the transmission of a series of refractions, all rectilinear, although otherwise susceptible of great varieties, as sometimes an inversion of the original objects, exhibiting them floating in the air, with other phenomena not less strange; which transmissions being imperceptible, may aggregately give the appearance of flexible rays.

Whether the apparent horizon at sea is a refracted line more elevated than the true horizon, is a question

SCIENTIFIC OBSERVATIONS.

293

worth determining, as if that is the case, all altitudes taken at sea must require a like correction on that account, independent of the correction which may be necessary for the refraction in altitude of the object observed. It seems probable also, that the refraction of the horizon may be liable to variation with the state of the atmosphere.

When the height of the observer above the level of the sea is known, the depression of the real terrestrial horizon is correctly ascertained on trigonometrical principles; accordingly, by observing the vertical arc contained between two opposite points of the apparent horizon, the refraction of the horizon can be determined, the difference of the observed vertical arc from the half circle being the combined effect of dip and refraction.

So much snow fell during the winter, that the Hollanders had almost every day to clear the entrance of their hut.

On the 13th of February, a great bear came close to their hut, which they shot, and obtained from the carcass above a hundredweight of fat or lard. On the 8th of March, the sea to the North was observed to be quite clear of ice, which made them conjecture there was a great extent of open sea in that direction. The next day the sea appeared equally open and clear to the North and North-East; but more eastward, and

to the S.E. there was ice; and to the South and S.E. they saw an appearance like land, but could not ascertain whether it was land or clouds.

In the night of April the 6th, during a thick fog, a bear came to the hut and endeavoured to force in the door. The Hollanders tried to shoot him, but, from the dampness of the weather, it was with much difficulty they could get one of their arquebuses to go off, which made the bear retire; but he returned in about two hours after, and mounting the roof of the hut, shook the chimney with all his might, endeavouring to pull it down, making at the same time a terrible roaring or noise. After much ineffectual trial, he went quietly

away.

Towards the end of May, they began to prepare their two boats, both open, with washboard, sails, &c., for their departure, as the only means for their escape from this desolate country. It was proposed to repass round the north end of Nova Zembla, in preference to seeking a passage southward on the East side, and that way through the Waigatz Strait. On the morning of June the 14th, they embarked in the two boats, with the remains of their provisions and some small packets of their best merchandise, and quitted the place where they had passed a winter of more than eight months' continuance.

Barentsz had been some time ill. One of the sea